The Cal 906 is the last automatic chronometer movement produced by the Manufacture.
In fact, JLC made 7000 Cal 906, since 1973, till 1975.
Some were housed in JLC watches, others were provided to Vacheron Constantin for their Chronometre Royal " automatic ".
According to the Heritage Gallery, 3060 Cal 906 were housed in 3 watch references: 24 000, 24 001 and 24 002, both being Chronometers.
The 24 000 was produced in 520 pieces, and in steel only.
The 24 001 was produced in 105 pieces in yellow gold, and 1050 pieces in steel.
The 24 002 was made in 234 pieces in yellow gold, and 1151 watches in steel.
All the 906 Chronometers have a screw in case back, with the word Chronometer engraved.
With these 24 000 / 24 001 and 24 002 references, the plexy is not used anymore, changed for a sapphire. A small change, announcing the modern times.
As for the movement, the Cal 906 is a 21 jewels automatic " engine ", quite brutal in its look, 28 mm big, 4, 65 mm high, beating at the pace of 28 800 alternances per hour, adjusted to 5 positions and temperatures.
It has a shock protection ( Kif Elastor ), a fine regulation system and a curious stop second, which is this blue plastic lever located close to the balance Wheel.
A last detail on this movement, the quick setting of the date, through pulling, then pushing the crown, which is a quite fragile system.
With the Cal 906 ends the Vintage Jaeger-Lecoultre Chronometer History... An History which will re born with the Master 1 000 Hours Control in 1992... But that is another story, which may soon have some further developments and chapters...
Best,